In the wireless communication field, spectrum resources are mainly categorized into licensed spectrum resources and unlicensed spectrum resources. In an existing Long Term Evolution (LTE) system, spectrum resources used by an operator are mainly licensed spectrum resources. As a quantity of users of a mobile communication network increases and the users' requirements on a communication rate and service quality get higher, existing licensed spectrum resources can hardly meet requirements of existing services of the operator. Having considered that new licensed spectra are high in price and short in resources, operators start to pay attention to unlicensed spectrum resources, expecting to achieve the purpose of offloading network capacities and improving service quality by using unlicensed spectrum resources.
Different countries or regions have specific requirements on use of unlicensed spectrum resources. For example, when sending a signal on an unlicensed spectrum resource, a device should follow a resource contention method of listen before talk (LBT). A maximum transmit power or a maximum transmit power spectrum density used by a device to send a signal on an unlicensed spectrum resource is restricted by laws and regulations. When a device sends a signal on an unlicensed spectrum resource, the signal needs to occupy 80% of a channel bandwidth.
In an existing LTE system, a terminal device (for example, User Equipment, UE) needs to send a random access preamble sequence on a physical random access channel (PRACH) resource during a random access process. A PRACH occupies six contiguous resource blocks (RB) in frequency domain. If an existing PRACH structure is used on an unlicensed spectrum resource, due to restrictions of laws and regulations, the requirement that the signal needs to occupy 80% of the channel bandwidth cannot be met, and a transmit power of the random access preamble sequence is restricted by a maximum transmit power spectrum density.
Therefore, to meet the foregoing requirements, a new PRACH structure and a new random access preamble sequence need to be designed.